a. Field of the Invention
The present invention pertains generally to integrated circuit technology and more particularly to the control of expanders.
b. Description of the Background
Expanders have been used to control the pulse shape, slew rate and timing of signals, such as SCSI signals, in computer systems. Expanders operate similarly to repeaters, but are capable of correcting the deleterious effects of impedance and delays that a system may have on pulse waveforms so as to greatly improve the operation of such systems. Expanders are capable of modifying pulse shape, slew rate and timing by using delay circuits, pulse shaping circuits and other technology. In this fashion, expanders have found great utility.
An optimal way of controlling an expander is to connect the expander directly to a host bus in the computer system and provide operational parameters from the host for operating the expander to provide the proper corrective factors at various places in a system. Some circuits are so complex that several expanders may be needed to provide the proper corrections. Since the host bus, which provides a communication channel for controlling various components in a system, only has a certain number of addresses to connect to these components, and the number of components that need to be connected to the host bus is numerous, connection of several expanders to the host bus may use too many of these limited number of addresses. If the expanders are not connected to the host bus, there is no apparent way to control the expanders by the host during validation and debugging. Since adjustments frequently need to be made to the operation of the expanders, as a result of actual circuit conditions, control of the expanders is needed.
To overcome these limitations EEPROM devices have been built into the expanders to provide the control bits that function as operational parameters to instruct the expander to provide the necessary corrections, as desired. However, to make these corrections, the EEPROMs must be reprogrammed to change the operation of the expander so as to provide different corrections to the computer system signals. This normally requires that the EEPROM be physically removed from the expander board, reprogrammed and then reinserted back into the expander board. This process is very time consuming and may need to be repeated several times to produce the proper corrective effects in the computer system signals.
Hence, it would be advantageous to provide a method and device for controlling the operation of the expander in a simple and easy manner without using an address location on the host bus.